Customer.statement():
public String statement() {
double totalAmount = 0;
int frequentRenterPoints = 0;
Enumeration rentals = _rentals.elements();
String result = "Rental Record for * " + getName() + "\n";
while(rentals.hasMoreElements()) {
double thisAmount = 0;
Rental each = (Rental)rentals.nextElement(); //取得一筆租借記錄
thisAmount = each.getCharge();
// add frequent renter points(累加常客積點)
frequentRenterPoints ++;
if((each.getMovie().getPriceCode() == Movie.NEW_RELEASE) &&
each.getDaysRented() > 1)
frequentRenterPoints ++;
result += "\t" + each.getMovie().getTitle() + "\t" +
String.valueOf(thisAmount) + "\n";
totalAmount += thisAmount;
}
// add footer lines(結尾打印)
result += "Amount owed is " + String.valueOf(totalAmount) + " \n";
result += "You earned " + String.valueOf(frequentRenterPoints) +
"frequent renter points";
return result;
}
下一件引我注意的事時:thisAmount如今變成多余了.它接受each.getCharge()的執行結果,然后就不再有任何改變.所以我可以運用Replace Temp with Query(120)把thisAmount除去:
public String statement() {
double totalAmount = 0;
int frequentRenterPoints = 0;
Enumeration rentals = _rentals.elements();
String result = "Rental Record for * " + getName() + "\n";
while(rentals.hasMoreElements()) {
Rental each = (Rental)rentals.nextElement(); //取得一筆租借記錄
// add frequent renter points(累加常客積點)
frequentRenterPoints ++;
if((each.getMovie().getPriceCode() == Movie.NEW_RELEASE) &&
each.getDaysRented() > 1)
frequentRenterPoints ++;
result += "\t" + each.getMovie().getTitle() + "\t" +
String.valueOf(each.getCharge()) + "\n";
totalAmount += each.getCharge();
}
// add footer lines(結尾打印)
result += "Amount owed is " + String.valueOf(totalAmount) + " \n";
result += "You earned " + String.valueOf(frequentRenterPoints) +
"frequent renter points";
return result;
}
我喜歡盡量除去這一類臨時變量.臨時變量往往形成問題.它們會導致大量參數被傳來傳
去,而其實完全沒有這種必要.你很容易失去它們的蹤跡,尤其在長長的函數之中更是如此.當然我這么做也需付出性能上的代價,例如本例的費用就被計算了兩
次.但是這很容易在Rental class中被優化.而且如果代碼有合理的組織和管理,優化會有很好的效果.